If one wants to short--buy and then sell the stock or buy a put. Selling someone else's stock or going into the float and selling stock you do not own is criminal. No wonder people not in the market liken us to a den of thieves. If I borrow your car without your permission and spend all day doing my chores with it, then return it to your driveway minus gas and a little ware and tear--I've committed a crime(here in california). I've devalued your vehicle like shorting devalues your stock(shares).